FLASH4.5 API

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[Functions] source/physics/sourceTerms/Heatexchange/Heatexchange_computeDt

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NAME

  Heatexchange_computeDt

SYNOPSIS

  Heatexchange_computeDt(integer(IN) :: blockID,
                 )
                 integer(IN) :: blkLimits(2,MDIM)
                 integer(IN) :: blkLimitsGC(2,MDIM)
                 real,pointer::  solnData(:,:,:,:),   
                 real(OUT)   :: dt_heatXchg, 
                 real(OUT)   :: dt_minloc(5)) 

DESCRIPTION

  compute a burning timestep limiter, by trying to force the energy
  generation from burning to be smaller than the internal energy
  in a zone.

   The timestep limiter would be:

                                      eintN
             dt     =  hx_dtFactor * ------
               burn                   qNdot

  qNdot is energy/mass/s, so the time factor is already in there, and we
  are doing

             
                                      eintN
             dt     =  hx_dtFactor * ------   * dt
               burn                   qNdot*dt

  qNdot*dt is the amount of energy / mass deposited in a zone by burning. 
  eintN is the internal energy / mass in that zone.  If qNdot*dt is 2x
  eintN, then we want a timestep that is half the size.  

  hx_dtFactor is a prefactor to scaling the timestep.  In general, we aim
  for qNdot*dt < hx_dtFactor * eintN.  For good coupling between the hydro
  and the burner, hx_dtFactor should be < 1.

ARGUMENTS

  blockID       --  local block ID
  
  blkLimits     --  the indices for the interior endpoints of the block
  blkLimitsGC   --  the indices for endpoints including the guardcells
  solnData      --  the physical, solution data from grid
  dt_heatXchg       --  variable to hold timestep constraint
  dt_minloc(5)  --  array to hold limiting zone info:  zone indices
                    (i,j,k), block ID, PE number

PARAMETERS

  hx_dtFactor    A parameter, such that qNdot*dt < hx_dtFactor * eint,
                  that is, the energy release from burning divided by
                  the internal energy in that zone is < hx_dtFactor.

SEE ALSO

  Driver_computeDt